Load responsive pressure transmitter



Nbv. 21, 1950 R. s. BOHANNAN 2,531,104

LOAD RESPONSIVE PRESSURE TRANSMITTER Filed Jan. 18, 1946 2 Sheets-Sheet1 INVENTOR. Fake/*7 J. Bafia/man Malia ATTORNEYS.

Nov. 21, 1950 R. s. BOHANNAN 2,531,104

LOAD RESPONSIVE PRESSURE TRANSMITTER Filed Jan. 18, 1946 2 Sheets-Sheet2 INVEN TOR.

E2, I 500W? 5. 60/20/2000 ATTORNEYS.

Patented Nov. 21, 1950 LOAD RESPONSIVE PRESSURE TRANSMITTER Robert S.Bohannan, Toledo, Ohio, assignor to Toledo Scale Company, Toledo, Ohio,a corporation of New Jersey Application January 18, 1946, Serial No.641,997

3 Claims. 1

This invention relates to hydraulic weighing scales and in particular toa simplified construction for the hydraulic load supporting elements.

When hydraulic force transmitting systems are used in weighing scales itis diiiicult to build a pressure transmitter which will accuratelytranslate load forces into hydraulic pressure without the capsulemechanicall contributing to the support of the load. Because thepressure receiver and load counterbalancing and indicating mechanism atthe other end of the hydraulic system is responsive onl to hydraulicpressure the indicating mechanism has no way of indicating the amount ofthe load mechanically supported by the pressure transmitter. It istherefore necessary that the pressure transmitters or capsules be soconstructed that either all of the force applied t them is convertedinto hydraulic pressure or that a precise nonvarying fractional part ofthe load be so translated. The second condition is practicall impossibleto attain or if once attained to maintain. Therefore, all of the loadmust be supported hydraulically and the sealing means employed toconfine the hydraulic fluid must be made as flexible as possible so thatits contribution to the support of the load is negligible. But flexiblesealing means or diaphragms are usually fragile and subject to leakageas well as being difiicult to install.

The object of the present invention is to provide a simplified sealinmeans for a hydraulic pressure transmitter which sealing means is simpleto install and is free from leakage. Another object of the invention isto provide a hydraulic capsule construction which may be easilydisassembled and assembled and in which the load forces are employed tohold the sealing means in liquid-tight engagement with the plates of thepressure transmitter.

These and other objects and advantages are apparent in the followingdescription in which reference is made to accompanying drawingsillustrating preferred embodiments of the invention.

According to the invention an improved hydraulic capsule for use intranslating load forces into hydraulic pressure may be constructed byinterposing an annular ieldable member between juxtaposed rigid plates.The plates are preferably circular in form although triangular, squareor other polygonal shapes may be employed. The yieldable member isinterposed between the peripheries of the plates so that a hydraulicchamber of substantial area is formed between the plates. The yieldablemember is preferabl an inflated rubber tube, although other yieldabletubes, a solid ring of one of the softer grades of rubber, or rings ofother cross-sectional configuration may be employed. To improvetheliquid seal between the plates and the sealing member the plates areprovided with grooves in their opposing faces adjacent theirperipheries, which grooves are of such size and shape as to accommodateportions of the sealing member without permitting the plates to contacteach other.

Hydraulic capsules constructed according to the invention are shown inthe accompanying drawings.

In the drawings? Figure I is a front elevation, partly in section andwith parts broken away, of a hydraulic Weighing scale. 7

Figure II is vertical section showing the con struction of the improvedhydraulic capsule.

Figure III is a plan view with parts broken away of the improvedcapsule.

Figure IV is a side elevation partly in section of a modified form ofthe invention.

These specific figures and the accompanying description are intendedmerely to illustrate preferred embodiments of the invention but not toimpose limitations on the claims.

A hydraulic weighing scale consists of a load receiver comprising a deck2 carried on longitudinally extending girders 3. The girders 3 at theirends are supported on plates 4 the lowermost of which are hollowed outto form shallow concave recesses 5. Each corner of the load receiver Iis supported from a hydraulic capsule 6 having a concave load supportingplate 1 on its upper surface. A steel ball 3 is interposed between theconcave portions of the plates 4 and l, the radius of the ball beingconsiderabl less than the concave recesses in the plates so that theload receiver i may have appreciable lateral freedom and yet will returnto its central position when the laterally deflecting forces areremoved. The load receiver and the capsules 6 are installed in aconcrete pit 9 with the decking 2 of the load receiver substantiallyflush with the surrounding area.

The capsules 5, designed to translate forces produced by loads on theload receiver I into hydraulic pressure, are individually connectedthrough pipes r tubes l0 leading upwardly through a hollow pedestal I!and connected to pressure receivers l2 mounted on a bracket I3 securedto the bottom of a weigh beam shelf l4. 'One end of the weigh beam shelf[4 surmounts a housing l5 which in turn rests on the 3 hollow pedestalH. The other end of the weigh beam shelf I4 is carried on a separatepost IS. The weigh beam shelf l4 ma be mounted either acjacent the loadreceiver l or at more remote locations, the lengths of the pipes IDbeing varied accordingly.

The hydraulic pressures transmitted through the pipes I are converted inthe pressure receivers l2 to forces which are transmitted throu h strutsI! to knife edges I8 mounted in a gathering lever l9. The lever i9 isfulcrumed in a depending portion of the bracket [3 attached to the weighbeam shelf l4. The lever 59 has a power pivot 29 mounted in anadjustable nose iron 2| and connected through stirrups 22 and asteelyard rod 23 to a load knife edge 24 mounted in a weigh beam 25. Theweigh beam 25 is fulcrumed on a fulcrum stand 26 erected from the weighbeam shelf M. The motion of the Weigh beam 25 is controlled or arrestedby a locking plate controlled by a handle 27 and mounted in a stand 28,the locking plate engaging a trip loop 29 formed in the end of the weighbeam 25. Load forces applied to the weigh beam 25 are counterbalanced bya poise 30 slidably mounted on the weigh beam 25. The scale may bebalanced at zero load by adjustment of counterweight 3i threaded on arod 32 secured to the weigh beam 25.

The capsules 5, serving as supports for the load receiver 1, eachcomprise a lower plate 33 and an upper plate 34. The lower and upperplates 33 and 34 are circular in shape and made of a rigid material.They are provided around their peripheries with grooves 35 and 36respectively. A rubber hose 3? cut to the length of the grooves 35 and36 and having its ends vulcanized together to form a ring is laid in thegroove 35 in the lower plate 33 and the upper plate 34 is placed on theassembly with the groove 36 overlying the hose 31. The hose 3'! may beinflated to cause it to maintain its shape under the static load of theupper plate 34. Hydraulic fluid confined in a chamber 38 between theplates 33 and 34 serves to support the major portion of a load appliedto the capsule. The hydraulic pressure generated in the chamber 38 byloads applied to the capsule is transmitted through drilled passages 39and coupling 40 to the associated one of the pipes It.

The cross-sectional shape of the grooves 35 and 35 is designed toconform to the surface of the hose 3? with each groove encompassingsubstantially more than a quarter but less than half of the periphery ofthe hose 31. Thus a substantial area for sealing the hydraulic fluid iobtained while still allowing the hose 3'! to yield and thereby permitthe load applied to the capsule to produce hydraulic pressure in thechamber 38.

It is possible that a capsule constructed with one hose may exhibit toomuch spring effect, i. e. support so much of the load by the resistanceto yielding of the hose 3'! that the hydraulic pressure is not a trueindication of the load on the capsule.

A capsule employing a hose as a sealing member depends upon the pressureexerted by the plates against the hose to keep the capsule from leaking.It may thus be said to be a pressure sealed capsule. The term pressuresealed is used to denote a separable structure which when assembled andin use is sealed by the forces exerted by the load. The structure isthus simplified over a conventional capsule in that no fluidtightclamped joints need be made.

A modified form of pressure sealed capsule is illustrated in Figure IV.The modified capsule comprises a lower plate 4| and an upper plate 42 towhich a recessed load supporting member 43 is attached. The capsuleplates 4| and 42 are provided with grooves 44 and t5 cut in theiropposing faces adjacent their peripheries, the grooves being bounded bysquare-shouldered rims 46 and 41. Molded rubber rings 48, U-shaped incross section, are interposed between the rims 46 and 41 with the openend of the U-shaped cross sections opening radially outwardly from thecapsule. The rubber rings 48 are fashioned with lips 49 and 50 adaptedto engage the square shoulders of the rims 46 and 41. When more than onesealing ring is used, rigid rings such as the ring 51 Which arerectangular in cross section are interposed between adjacent rubbersealing rings. While two rubber rings are shown the capsule may beconstructed of any reasonable number because the pressures exertedbetween the rubber sealing rings and the adjacent rigid members istransmitted from one set of sealing members to the next ring in much thesame manner as tensile forces are transmitted from link to link througha chain.

Because the resistance to deformation of the sealing rings having theU-shaped cross section is. materially less than that of the hose typesealing members it is necessary to cement the sides of the rings to theadjacent rigid parts of the capsule. The cementing prevents the hydraulic fiuid from penetrating into the joint between the rubber ringsand the capsule plates or rings and forcing the rubber rings out ofcontact with the plates. The lips 63 and 58 serve to position the ringsbetween the capsule plates and to prevent the fluid from pushing therings out of position. When the capsule plates 4! and 42 are assembledwith the sealing rings 48 a hydraulic chamber 52 is formed between theplates. Hydraulic fiuid confined in the chamber 52 serves to support themajor part of the load applied to the capsule and the pressure developedin the hydraulic fluid in response to the load is transmitted throughdrilled passages 53 and a coupling 54 to a pipe 55 leading to a pressurereceiver operatively connected to counterbalancing and indicatingmechanism.

The improved sealing means embodying the invention of which preferredforms are illustrated in the drawings make extensive clampingunnecessary in constructing a hydraulic pressure transmitter. Thissimplification makes it comparatively easy to rebuild a capsule whichmay require servicing because the parts are held in operative relationprimarily by the load forces being supported by the capsule.

Having described the invention, I claim:

1. A hydraulic capsule for use in a weighing scale, the capsulecomprising a pair of plates separated by a hydraulic fluid, a hose-likeyieldable member interposed between the peripheries of the plates andheld in fluid-tight engagement by load forces applied to the capsule,and means for hydraulically connecting the space between the plates to apressure receiver.

2. A hydraulic capsule for use in a weighing scale, the capsulecomprisin a pair of plates separated by a hydraulic fiuid, an inflatedhose held interposed between the peripheries of the plates by loadforces to confine the hydraulic fluid, and means for hydraulicallyconnecting the space between the plates to a pressure receiver.

3. A pressure transmitter for a hydraulic weighing scale, thetransmitter comprising a REFERENCES CITED pair of plates each having agroove cut The following references are of record in the face near itsperiphery, the grooves being 1n file of this patent:

registry when the plates are juxtaposed, a yieldable member interposedbetween the plates and 5 UNITED STATES PATENTS having portions lying inthe grooves for con- Number Name Date fining hydraulic fluid in thespace between the 1,446,439 Lieberman Feb. 20, 1923 plates, and meansfor hydraulically connecting a 2,096,066 Saforcada Oct. 19, 1937pressure receiver to the space between the plates. 2,411,251 Feld Nov.19, 1946 ROBERT S. BOHANNAN. 10

